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Support: Extract ScaledNumbers::getSum() and getDifference()

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211553 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Duncan P. N. Exon Smith 2014-06-23 23:15:25 +00:00
parent 465f06cfa6
commit 558b7725b7
3 changed files with 250 additions and 61 deletions
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74
include/llvm/Analysis/BlockFrequencyInfoImpl.h
View File

@ -229,8 +229,19 @@ public:
}
void dump() const { return UnsignedFloatBase::dump(Digits, Exponent, Width); }
UnsignedFloat &operator+=(const UnsignedFloat &X);
UnsignedFloat &operator-=(const UnsignedFloat &X);
UnsignedFloat &operator+=(const UnsignedFloat &X) {
std::tie(Digits, Exponent) =
ScaledNumbers::getSum(Digits, Exponent, X.Digits, X.Exponent);
// Check for exponent past MaxExponent.
if (Exponent > MaxExponent)
*this = getLargest();
return *this;
}
UnsignedFloat &operator-=(const UnsignedFloat &X) {
std::tie(Digits, Exponent) =
ScaledNumbers::getDifference(Digits, Exponent, X.Digits, X.Exponent);
return *this;
}
UnsignedFloat &operator*=(const UnsignedFloat &X);
UnsignedFloat &operator/=(const UnsignedFloat &X);
UnsignedFloat &operator<<=(int16_t Shift) { shiftLeft(Shift); return *this; }
@ -399,65 +410,6 @@ IntT UnsignedFloat<DigitsT>::toInt() const {
return N;
}
template <class DigitsT>
UnsignedFloat<DigitsT> &UnsignedFloat<DigitsT>::
operator+=(const UnsignedFloat &X) {
if (isLargest() || X.isZero())
return *this;
if (isZero() || X.isLargest())
return *this = X;
// Normalize exponents.
UnsignedFloat Scaled = matchExponents(X);
// Check for zero again.
if (isZero())
return *this = Scaled;
if (Scaled.isZero())
return *this;
// Compute sum.
DigitsType Sum = Digits + Scaled.Digits;
bool DidOverflow = Sum < Digits;
Digits = Sum;
if (!DidOverflow)
return *this;
if (Exponent == MaxExponent)
return *this = getLargest();
++Exponent;
Digits = UINT64_C(1) << (Width - 1) | Digits >> 1;
return *this;
}
template <class DigitsT>
UnsignedFloat<DigitsT> &UnsignedFloat<DigitsT>::
operator-=(const UnsignedFloat &X) {
if (X.isZero())
return *this;
if (*this <= X)
return *this = getZero();
// Normalize exponents.
UnsignedFloat Scaled = matchExponents(X);
assert(Digits >= Scaled.Digits);
// Compute difference.
if (!Scaled.isZero()) {
Digits -= Scaled.Digits;
return *this;
}
// Check if X just barely lost its last bit. E.g., for 32-bit:
//
// 1*2^32 - 1*2^0 == 0xffffffff != 1*2^32
if (*this == UnsignedFloat(1, X.lgFloor() + Width)) {
Digits = DigitsType(0) - 1;
--Exponent;
}
return *this;
}
template <class DigitsT>
UnsignedFloat<DigitsT> &UnsignedFloat<DigitsT>::
operator*=(const UnsignedFloat &X) {

87
include/llvm/Support/ScaledNumber.h
View File

@ -317,6 +317,93 @@ int16_t matchScales(DigitsT &LDigits, int16_t &LScale, DigitsT &RDigits,
return LScale;
}
/// \brief Get the sum of two scaled numbers.
///
/// Get the sum of two scaled numbers with as much precision as possible.
///
/// \pre Adding 1 to \c LScale (or \c RScale) will not overflow INT16_MAX.
template <class DigitsT>
std::pair<DigitsT, int16_t> getSum(DigitsT LDigits, int16_t LScale,
DigitsT RDigits, int16_t RScale) {
static_assert(!std::numeric_limits<DigitsT>::is_signed, "expected unsigned");
// Check inputs up front. This is only relevent if addition overflows, but
// testing here should catch more bugs.
assert(LScale < INT16_MAX && "scale too large");
assert(RScale < INT16_MAX && "scale too large");
// Normalize digits to match scales.
int16_t Scale = matchScales(LDigits, LScale, RDigits, RScale);
// Compute sum.
DigitsT Sum = LDigits + RDigits;
if (Sum >= RDigits)
return std::make_pair(Sum, Scale);
// Adjust sum after arithmetic overflow.
DigitsT HighBit = DigitsT(1) << (getWidth<DigitsT>() - 1);
return std::make_pair(HighBit | Sum >> 1, Scale + 1);
}
/// \brief Convenience helper for 32-bit sum.
inline std::pair<uint32_t, int16_t> getSum32(uint32_t LDigits, int16_t LScale,
uint32_t RDigits, int16_t RScale) {
return getSum(LDigits, LScale, RDigits, RScale);
}
/// \brief Convenience helper for 64-bit sum.
inline std::pair<uint64_t, int16_t> getSum64(uint64_t LDigits, int16_t LScale,
uint64_t RDigits, int16_t RScale) {
return getSum(LDigits, LScale, RDigits, RScale);
}
/// \brief Get the difference of two scaled numbers.
///
/// Get LHS minus RHS with as much precision as possible.
///
/// Returns \c (0, 0) if the RHS is larger than the LHS.
template <class DigitsT>
std::pair<DigitsT, int16_t> getDifference(DigitsT LDigits, int16_t LScale,
DigitsT RDigits, int16_t RScale) {
static_assert(!std::numeric_limits<DigitsT>::is_signed, "expected unsigned");
// Normalize digits to match scales.
const DigitsT SavedRDigits = RDigits;
const int16_t SavedRScale = RScale;
matchScales(LDigits, LScale, RDigits, RScale);
// Compute difference.
if (LDigits <= RDigits)
return std::make_pair(0, 0);
if (RDigits || !SavedRDigits)
return std::make_pair(LDigits - RDigits, LScale);
// Check if RDigits just barely lost its last bit. E.g., for 32-bit:
//
// 1*2^32 - 1*2^0 == 0xffffffff != 1*2^32
const auto RLgFloor = getLgFloor(SavedRDigits, SavedRScale);
if (!compare(LDigits, LScale, DigitsT(1), RLgFloor + getWidth<DigitsT>()))
return std::make_pair(std::numeric_limits<DigitsT>::max(), RLgFloor);
return std::make_pair(LDigits, LScale);
}
/// \brief Convenience helper for 32-bit sum.
inline std::pair<uint32_t, int16_t> getDifference32(uint32_t LDigits,
int16_t LScale,
uint32_t RDigits,
int16_t RScale) {
return getDifference(LDigits, LScale, RDigits, RScale);
}
/// \brief Convenience helper for 64-bit sum.
inline std::pair<uint64_t, int16_t> getDifference64(uint64_t LDigits,
int16_t LScale,
uint64_t RDigits,
int16_t RScale) {
return getDifference(LDigits, LScale, RDigits, RScale);
}
} // end namespace ScaledNumbers
} // end namespace llvm

150
unittests/Support/ScaledNumberTest.cpp
View File

@ -386,4 +386,154 @@ TEST(ScaledNumberHelpersTest, matchScales) {
MATCH_SCALES(uint64_t, 9, 0, UINT64_C(1) << 59, 4, 9, UINT64_C(1) << 63, 0);
}
TEST(ScaledNumberHelpersTest, getSum) {
// Zero.
EXPECT_EQ(SP32(1, 0), getSum32(0, 0, 1, 0));
EXPECT_EQ(SP32(8, -3), getSum32(0, 0, 8, -3));
EXPECT_EQ(SP32(UINT32_MAX, 0), getSum32(0, 0, UINT32_MAX, 0));
// Basic.
EXPECT_EQ(SP32(2, 0), getSum32(1, 0, 1, 0));
EXPECT_EQ(SP32(3, 0), getSum32(1, 0, 2, 0));
EXPECT_EQ(SP32(67, 0), getSum32(7, 0, 60, 0));
// Different scales.
EXPECT_EQ(SP32(3, 0), getSum32(1, 0, 1, 1));
EXPECT_EQ(SP32(4, 0), getSum32(2, 0, 1, 1));
// Loss of precision.
EXPECT_EQ(SP32(UINT32_C(1) << 31, 1), getSum32(1, 32, 1, 0));
EXPECT_EQ(SP32(UINT32_C(1) << 31, -31), getSum32(1, -32, 1, 0));
// Not quite loss of precision.
EXPECT_EQ(SP32((UINT32_C(1) << 31) + 1, 1), getSum32(1, 32, 1, 1));
EXPECT_EQ(SP32((UINT32_C(1) << 31) + 1, -32), getSum32(1, -32, 1, -1));
// Overflow.
EXPECT_EQ(SP32(UINT32_C(1) << 31, 1), getSum32(1, 0, UINT32_MAX, 0));
// Reverse operand order.
EXPECT_EQ(SP32(1, 0), getSum32(1, 0, 0, 0));
EXPECT_EQ(SP32(8, -3), getSum32(8, -3, 0, 0));
EXPECT_EQ(SP32(UINT32_MAX, 0), getSum32(UINT32_MAX, 0, 0, 0));
EXPECT_EQ(SP32(3, 0), getSum32(2, 0, 1, 0));
EXPECT_EQ(SP32(67, 0), getSum32(60, 0, 7, 0));
EXPECT_EQ(SP32(3, 0), getSum32(1, 1, 1, 0));
EXPECT_EQ(SP32(4, 0), getSum32(1, 1, 2, 0));
EXPECT_EQ(SP32(UINT32_C(1) << 31, 1), getSum32(1, 0, 1, 32));
EXPECT_EQ(SP32(UINT32_C(1) << 31, -31), getSum32(1, 0, 1, -32));
EXPECT_EQ(SP32((UINT32_C(1) << 31) + 1, 1), getSum32(1, 1, 1, 32));
EXPECT_EQ(SP32((UINT32_C(1) << 31) + 1, -32), getSum32(1, -1, 1, -32));
EXPECT_EQ(SP32(UINT32_C(1) << 31, 1), getSum32(UINT32_MAX, 0, 1, 0));
// Zero.
EXPECT_EQ(SP64(1, 0), getSum64(0, 0, 1, 0));
EXPECT_EQ(SP64(8, -3), getSum64(0, 0, 8, -3));
EXPECT_EQ(SP64(UINT64_MAX, 0), getSum64(0, 0, UINT64_MAX, 0));
// Basic.
EXPECT_EQ(SP64(2, 0), getSum64(1, 0, 1, 0));
EXPECT_EQ(SP64(3, 0), getSum64(1, 0, 2, 0));
EXPECT_EQ(SP64(67, 0), getSum64(7, 0, 60, 0));
// Different scales.
EXPECT_EQ(SP64(3, 0), getSum64(1, 0, 1, 1));
EXPECT_EQ(SP64(4, 0), getSum64(2, 0, 1, 1));
// Loss of precision.
EXPECT_EQ(SP64(UINT64_C(1) << 63, 1), getSum64(1, 64, 1, 0));
EXPECT_EQ(SP64(UINT64_C(1) << 63, -63), getSum64(1, -64, 1, 0));
// Not quite loss of precision.
EXPECT_EQ(SP64((UINT64_C(1) << 63) + 1, 1), getSum64(1, 64, 1, 1));
EXPECT_EQ(SP64((UINT64_C(1) << 63) + 1, -64), getSum64(1, -64, 1, -1));
// Overflow.
EXPECT_EQ(SP64(UINT64_C(1) << 63, 1), getSum64(1, 0, UINT64_MAX, 0));
// Reverse operand order.
EXPECT_EQ(SP64(1, 0), getSum64(1, 0, 0, 0));
EXPECT_EQ(SP64(8, -3), getSum64(8, -3, 0, 0));
EXPECT_EQ(SP64(UINT64_MAX, 0), getSum64(UINT64_MAX, 0, 0, 0));
EXPECT_EQ(SP64(3, 0), getSum64(2, 0, 1, 0));
EXPECT_EQ(SP64(67, 0), getSum64(60, 0, 7, 0));
EXPECT_EQ(SP64(3, 0), getSum64(1, 1, 1, 0));
EXPECT_EQ(SP64(4, 0), getSum64(1, 1, 2, 0));
EXPECT_EQ(SP64(UINT64_C(1) << 63, 1), getSum64(1, 0, 1, 64));
EXPECT_EQ(SP64(UINT64_C(1) << 63, -63), getSum64(1, 0, 1, -64));
EXPECT_EQ(SP64((UINT64_C(1) << 63) + 1, 1), getSum64(1, 1, 1, 64));
EXPECT_EQ(SP64((UINT64_C(1) << 63) + 1, -64), getSum64(1, -1, 1, -64));
EXPECT_EQ(SP64(UINT64_C(1) << 63, 1), getSum64(UINT64_MAX, 0, 1, 0));
}
TEST(ScaledNumberHelpersTest, getDifference) {
// Basic.
EXPECT_EQ(SP32(0, 0), getDifference32(1, 0, 1, 0));
EXPECT_EQ(SP32(1, 0), getDifference32(2, 0, 1, 0));
EXPECT_EQ(SP32(53, 0), getDifference32(60, 0, 7, 0));
// Equals "0", different scales.
EXPECT_EQ(SP32(0, 0), getDifference32(2, 0, 1, 1));
// Subtract "0".
EXPECT_EQ(SP32(1, 0), getDifference32(1, 0, 0, 0));
EXPECT_EQ(SP32(8, -3), getDifference32(8, -3, 0, 0));
EXPECT_EQ(SP32(UINT32_MAX, 0), getDifference32(UINT32_MAX, 0, 0, 0));
// Loss of precision.
EXPECT_EQ(SP32((UINT32_C(1) << 31) + 1, 1),
getDifference32((UINT32_C(1) << 31) + 1, 1, 1, 0));
EXPECT_EQ(SP32((UINT32_C(1) << 31) + 1, -31),
getDifference32((UINT32_C(1) << 31) + 1, -31, 1, -32));
// Not quite loss of precision.
EXPECT_EQ(SP32(UINT32_MAX, 0), getDifference32(1, 32, 1, 0));
EXPECT_EQ(SP32(UINT32_MAX, -32), getDifference32(1, 0, 1, -32));
// Saturate to "0".
EXPECT_EQ(SP32(0, 0), getDifference32(0, 0, 1, 0));
EXPECT_EQ(SP32(0, 0), getDifference32(0, 0, 8, -3));
EXPECT_EQ(SP32(0, 0), getDifference32(0, 0, UINT32_MAX, 0));
EXPECT_EQ(SP32(0, 0), getDifference32(7, 0, 60, 0));
EXPECT_EQ(SP32(0, 0), getDifference32(1, 0, 1, 1));
EXPECT_EQ(SP32(0, 0), getDifference32(1, -32, 1, 0));
EXPECT_EQ(SP32(0, 0), getDifference32(1, -32, 1, -1));
// Regression tests for cases that failed during bringup.
EXPECT_EQ(SP32(UINT32_C(1) << 26, -31),
getDifference32(1, 0, UINT32_C(31) << 27, -32));
// Basic.
EXPECT_EQ(SP64(0, 0), getDifference64(1, 0, 1, 0));
EXPECT_EQ(SP64(1, 0), getDifference64(2, 0, 1, 0));
EXPECT_EQ(SP64(53, 0), getDifference64(60, 0, 7, 0));
// Equals "0", different scales.
EXPECT_EQ(SP64(0, 0), getDifference64(2, 0, 1, 1));
// Subtract "0".
EXPECT_EQ(SP64(1, 0), getDifference64(1, 0, 0, 0));
EXPECT_EQ(SP64(8, -3), getDifference64(8, -3, 0, 0));
EXPECT_EQ(SP64(UINT64_MAX, 0), getDifference64(UINT64_MAX, 0, 0, 0));
// Loss of precision.
EXPECT_EQ(SP64((UINT64_C(1) << 63) + 1, 1),
getDifference64((UINT64_C(1) << 63) + 1, 1, 1, 0));
EXPECT_EQ(SP64((UINT64_C(1) << 63) + 1, -63),
getDifference64((UINT64_C(1) << 63) + 1, -63, 1, -64));
// Not quite loss of precision.
EXPECT_EQ(SP64(UINT64_MAX, 0), getDifference64(1, 64, 1, 0));
EXPECT_EQ(SP64(UINT64_MAX, -64), getDifference64(1, 0, 1, -64));
// Saturate to "0".
EXPECT_EQ(SP64(0, 0), getDifference64(0, 0, 1, 0));
EXPECT_EQ(SP64(0, 0), getDifference64(0, 0, 8, -3));
EXPECT_EQ(SP64(0, 0), getDifference64(0, 0, UINT64_MAX, 0));
EXPECT_EQ(SP64(0, 0), getDifference64(7, 0, 60, 0));
EXPECT_EQ(SP64(0, 0), getDifference64(1, 0, 1, 1));
EXPECT_EQ(SP64(0, 0), getDifference64(1, -64, 1, 0));
EXPECT_EQ(SP64(0, 0), getDifference64(1, -64, 1, -1));
}
} // end namespace